1. Field of the Disclosure
This disclosure relates generally to apparatus and methods for completing a wellbore for the production of hydrocarbons from subsurface formations, including fracturing selected formation zones in a wellbore, sand packing and flooding a formation with a fluid.
2. Background of the Art
Wellbores are drilled in subsurface formations for the production of hydrocarbons (oil and gas). Modern wells can extend to great well depths, often more than 1500 meters (about 15,000 ft.). Hydrocarbons are trapped in various traps in the subsurface formations at different depths. Such sections of the formation are referred to as reservoirs or hydrocarbon-bearing formations or zones. Some formations have high mobility, which is a measure of the ease of the hydrocarbons flow from the reservoir into a well drilled through the reservoir under natural downhole pressures. Some formations have low mobility and the hydrocarbons trapped therein are unable to move with ease from the reservoir into the well. Stimulation methods are typically employed to improve the mobility of the hydrocarbons through the reservoirs. One such method, referred to as fracturing (also referred to as “fracing” or “fracking”), is often utilized to create cracks in the reservoir to enable the fluid from the formation (formation fluid) to flow from the reservoir into the wellbore. To fracture multiple zones, an assembly containing an outer string with an inner string therein is run in or deployed in the wellbore. The outer string typically includes a screen placed proximate to the perforations. The inner string includes a crossover. To fracture a formation, a fluid is supplied under pressure from the inner string to the formation via the annular space between the screen and the casing through the perforations. Typically a certain minimum width of the annular space is required for the proper flow of the fluid through the perforations, which may be of the order of one half of an inch or more. The screen is left in the casing after fracturing for flow of reservoir fluid into the casing. The fracturing fluid typically contains a proppant, such as sand, which is corrosive to the screen. Also, it is desirable to reduce the width of the annular space so as to have as increased inside diameter of the casing for production of hydrocarbons from the reservoir.
The disclosure herein, in one aspect, provides an annular space outside of the casing for supplying treatment fluid to the formation, substantially bypassing the screen.